Telephone system



April 8, 1941. N. H. SAUNDERS TELEPHONE SYSTEM 3 Sheets-Sheet 1 Original Filed June 8 1932 tuba! H E In\.r' ihTEr' Nut-min H- 5 lundlr I d I v 5% April 8, 1941. SAUNDERS TELEPHONE SYSTEM Original Filed June 8, 195 2 3 sheets sheet 2 1% I EQ N 8N a 5 a? a .8: H.- QN H w I g w w m k N .I QNN Jr W 3 8w N mnml l k. NOiQ Q25 April 8, 1941. N. H. SAUNDERS TELEPHONE SYSTEM Original Filed June 8 193 2 3 Sheets-Sheet 3 In Nur-man H. Saunders q&

Reiuued Apr. 8, 1941 TELEPHONE SYSTEM Norman 1!. Saunders, Chicago, Ill., assignor, by mesne assignments, to Associated Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Original No. 1,971,505, dated August 28, 1934, Se-

rial No. 615,970, June 8, 1932.

Application for reissue June 5,1940, Serial No. 338,999

41 Claim.

This invention relates to telephone systems in general and particularly to telephone systems in which connections are completed through the medium of automatic switches. The object of the invention is to improve the switching apparatus required for the establishment of local and toil connections in such systems.

General description The switch train to which the improved features of the invention have been applied include toll selectors and combination local and toll connectors. These switches are adapted to cooperate with other well known switching apparatus and to constitute therewith a complete automatic telephone exchange system.

The toll selectors have been improved by the introduction of a more efficient and reliable testing circuit wherein a polarized relay tests for a definite potential to indicate an idle trunk. Another featureds the arrangement for registering the number of calls attempted to trunk groups in which all trunks are engaged. A further feature is the arrangement for switching over from the primary to the secondary operating stage.

The connectors have been improved by the introduction of a more reliable testing circuit for determining the idle or busy condition of the called lines. Another feature is the improved wiper-selecting arrangement for determining which one of two sets of wipers is to be used in a connection. Another feature is the arrangement for switching over from one operating stage to the succeeding operating stage.

Another feature is the arrangement which permits the ground conection to the battery-teed relay to be kept open when the connectors are not in use. thereby preventing electrolytic action in the relay winding. A further feature is the arrangement for controlling the supervisory signals according to the class 'of connection extended over a connector.

While the various features above discussed have been illustrated in conection with specific types of switches, it will be appreciated that certain of these features have a much wider application. The scope of the invention accordingly is not limited by the particular embodiment in which it has been shown, but is defined in the appended claims.

Description of drawings The accompanying drawings comprising Figs.

1 to 3, inclusive, show sufficient circuits of a system embodying the invention to permit the same to be readily explained and understood.

Fig. 1 shows a toll operators cord circuit C, a toll-transmission selector TS, and a toll-intermediate selector IS.

Fig. 2 shows a combination local and toll connector C for extending connections to individual lines.

Fig. 3 shows a combination local and toll connector CI for extending connections to party lines. 9

Referring now to Fig. 1 there is shown the calling end of an ordinary cord circuit C. The cord circuit of which only a part is shown may be of any suitable type provided with a polarized relay for controlling the supervisory signals. The cord is provided with a plug P for connecting the same with trunks extending to transmission selectors, such as the selector TS, at the automatic exchange. The selector TS which is a two-motion Strowger switch, has access to trunks extending to toll-intermediate selectors of which the selector IS has been shown. Both of the toll selectors are provided with testing relays of the type disclosed in Pye Patent No. 1,673,884, granted June 19, 1928. The characteristics of these relays are clearly described in the patent and will be discussed in detail hereinafter. The intermediate selector IS and other similar selectors have access, together with the local selectors of the automatic ofiice, to trunks extending to combination local and toll connectors, such as those shown in Figs. 2 and 3.

Connector C shown in Fig. 2 is accessible over the two branches of the incoming toll-intermediate selectors, local selectors, respectively. The operating characteristics of the switch are determined by the route over which a connection is extended thereto. The switch is equipped with two separate sets of wipers and accordingly has access to two hundred different subscribers lines. Wiper selection is controlled by relays in the switch which respond to impulses dialled by a calling subscriber or operator.

In Fig. 3, there is shown a combination local and toil party line connector Cl, which is accessible to toll selectors and local selectors over separate branches of the incoming trunk, respectively. This switch also operates as a local or a toll switch, depending on the route over which a connection is extended thereto. The switch is provided with two separate sets of wipers which give it access to two hundred different party lines. Wiper selection as well as ringing current selection is made by means an auxiliary switch associated with the connector.

Detailed description The operations involved in establishing various types of connections over the circuits illustratedinthe drawingswillnowbedescribcdin detail to more clearly bring out the novel teatures of the invention.

Initiation of a toll call It will be assumed for the purpose of this descriptlon that the toll operator has received a toll call for the subscriber at substation T (Fig. 2), and that she has selected the cord circuit C for extending the connection. The plug P is then inserted into the jack J of an idle trunk, such as the trunk comprising conductors I and I, which terminates in transmission selector TS. Line relay l I 01 the transmission selector is energized over a circuit which may be traced from battery, upper winding of the relay, vertical olfnormal contacts II, contacts 2! and 28, resistance, lower left-hand winding of repeating coil R, trunk conductor 5, tip contacts of the jack and plug, upper normally closed contacts of the key K, winding oi polarized relay I, lower contacts oi the key K, ring contacts of the plug and jack, trunk conductor 3, upper left-hand winding of repeating coil B, through the resistance and contacts II to ground. Relay I does not operate at this time due to the direction of current flow in its winding. Relay II on operating completes an obvious circuit for relay I! at contacts 40. Relay II, which is provided with a copper sleeve to make it slow-releasing, operates, short-circuits ofl-normai contacts I at its upper contacts, prepares the impulsing circuit at contacts l2, prepares the test circuit at contacts ll, and at contacts completes circuits for the lower winding of relays 5 and II. The circuit of relay 5 includes contacts 54, eleventh position contacts RC, and contacts and the lower winding 01 the relay. Relay l3 whose upper winding is connected in parallel with relay I! by way of contacts 52 and vertical oil-normal contacts l'l, operates and prepares a circuit for its lower winding and the vertical magnet in parallel at contacts 4!. Relay 5 operates over the circuit above traced and opens a point in the circuit of relay Ii at its upper contacts. The transmission selector is now ready to respond to impulses from the operator's calling device.

Setting the selectors The calling operator now operats key K to the right, thereby bridging the calling device CD across the trunk conductors in place of the polarized relay I. The operator then dials the first digit of the called number, interrupting the circuit of line relay II at interrupter contacts 2 of the calling device CD. Relay ll responds in the usual way and transmits a corresponding series of impulses by way of contacts II, II, and 49 to vertical magnet VM and the lower winding of relay l3. The vertical magnet raises the wipers step-by-step to the called level. The offnormal contacts VON operate on the first vertical step of the wipers and the original energizing circuit of relay I3 is opened at contacts l1. Relay I3 is slow releasing, however, and the impulses received by the lower winding maintain the relay operated throughout the series of impulses. It will also be noted that the original ill energizing circuit of relay II is opened at oilnonnal contacts it, however, a new circuit for the relay is maintained over the upper contacts of the relay l2.

Shortly after the last impulse of the series, relay l3 releases and completes a circuit for the rotary magnet RM by way of contacts ll, contacts 52, vertical oft-normal contacts I, contacts 48, and interrupter contacts 52. The rotary magnet energizes and steps the wipers in on the first set 01' contacts in the called level. The selector new tests for the idle or busy condition oi the trunk terminating in this set of contacts. As previously stated, the lower winding of relay ll was energized when relay l2 operated. Relay ll does not operate over its lower winding alone and requires a specific potential on its upper winding to bring about its energimtion. This potential in the present instance is battery through the low-resistance winding of a relay in the switch ahead. Assuming that the trunk is busy either due to the prior seizure by another switch or due to the operation oi the busy key of the switch associated with the trunk which opens the test circuit. relay II will find no operating potential and consequently will not operate. The rotary magnet, upon energizing as described, opened its own circuit at contacts 62 and, upon deenergizing it again closes its circuit so that it now reoperates and advances the wipers a second step. This buzzer-like action continues until an idle trunk is found, which, for example, may be the trunk comprising conductors 5356 terminating in intermediate selector IS. When the wipers engage the contacts terminating this trunk a circuit is completed from battery through the low resistance upper winding of relay 14, vertical oil-normal contacts 69, busy-key contacts BK, release trunk conductor 54, test contact and wiper 55, upper winding of polarized relay I4 and contacts H to ground. Relay It operates very quickly under these conditions and opens the rotary magnet circuit at contacts 52. Direct ground is applied to the test wiper by way of contacts 53 and the two windings of the relay are connected in series and a control circuit is extended from the transmission selector to the intermediate selector.

In the selector IS relay ll operates from ground on the release trunk and prepares various circuits including a circuit for its own lower winding and vertical magnet VM in parallel at contacts 80. A circuit is also completed for line relay [2 of selector IS which may be traced from battery, upper winding of the relay, eleventh position rotary contacts 51, contacts 85, trunk conductor 53, wiper 58 of transmission selector TS, upper contacts of relays II and II, contacts 32, upper right-hand winding of repeating coil R, contacts 23, upper winding of relay 5, lower right-hand winding of repeating coil R, contacts 35 and 55, wiper 5|, trunk conductor 55, contacts 92, lower winding 01 relay 1?, contacts I3 and 89 to ground. The initial energizing circuit of relay 5 was opened at contacts 5| upon the operation of relay II and the relay is now energized in series with relay 12 of selector IS. Relay 12 operates in series with the upper winding of relay 5 and completes an obvious circuit for relay 13 at contacts l5. Relay 13 operates, applies ground to release-trunk conductor 64 at its upper contacts, prepares the impuising circuit at contacts II and completes a circuit for the lower winding of polarized relay 1| at its lower contacts. Relay 1| does not operate at this time.

The operator now dials the second digit of the called number and relay ll responds as in the previous instance. The loop circuit previously traced for the impulse relay oi the intermediate selector is interrupted at the upper contacts of relay ii and the impulse relay responds accordingly. The circuit of relay 6 is also opened for each impulse but this relay does not restore during the lmpulsing as it is slow-releasing due to the copper sleeve and copper sing on its core. Relay 12 responds to the impulses and transmits a corresponding series of impulses by way of contacts 00, 11, 18, and to vertical magnet VM, and the lower winding of slow-releasing relay 14. The vertical magnet raises the wipers to the level indicated by the series of impulses. Relay 1 remains energized throughout the series of impulses due to the impulses received by its lower winding although its initial energizing circuit is opened at vertical cit-normal contacts 00 when the wipers leave normal position. Shortly after the last impulse of the series, relay 1| restores and completes the circuit of the rotary magnet at its upper contacts. The rotary magnet energizes, steps the wipers in on the first set of the contacts of the called level, and interrupts its own circuit at its interrupter contacts. The selector tests for an idle trunk in exactly the same manner as described for the transmission selector, and when such trunk is found, polarized relay 15 energizes and opens the rotary magnet circuit at contacts 09. Impulse relay 12 is disconnected from the loop at contacts 00 and 92 and the loop is extended by way oi contacts 06 and 9| and wipers 93 and 96 to the line relay oi the succeeding switch. The upper winding of relay 1! is short-circuited at contacts 21 and the control conductor is connected by way of contacts 90 to wiper 95.

Assume for example that the trunk selected is the trunk comprising conductors 2I0--22l terminating in connector C (Fig. 2). The control loop of the transmission selector is extended over the upper and lower wipers of the intermediate selector and thence over trunk conductors 2! and 22i, contacts 222, 229, 232, and 230 to the upper and lower winding of relay 203. The upper winding of relay 203 has battery normally connected thereto. The lower winding of this relay is connected to the release trunk conductor of the switch to which ground is now connected by way of busying key contacts H1 and HG, vertical oil-normal contacts 2l2, test conductor 2, test wiper 04 of switch IS, contacts 81 and the upper contacts of relay 13. Relay 203 operates in the above circuit and completes a circuit for relay at contacts 231. The ground on the release trunk also energizes relay 200 which prepares a holding circuit for itself and connects vertical magnet VM to the impulse circuit of the connector. Relay 204 operates and connects ground directly to the lower winding oi relay 203 at its upper contacts, prepares the lmpulsing circuit at contacts 240 and opens the release magnet circuit at its lower contacts.

setting connector C The operator now dials the third digit of the called number and relay ll of the transmission switch selector repeats these impulses to relay 202 of the connector. Relay 203 in turn transmits impulses by way of contacts 230, 210, lower contacts of relay 200, contacts 212 and 2". winding oi the vertical magnet to battery. The vertical magnet responds to the impulses and raises the wipers step-by-step to the called level. Relay 201. which is connected in parallel with the magnet operates in response to the first impulse and remains operated throughout the series of impulses. Relay 201 by closing contacts 200 completes a circuit for maintaining relay 200 energized when its original energizing circuit is opened at oil-normal contacts 2. Relay 201 also completes a circuit for the lower winding oi relay 200 byclosing its lower contacts'. The circuit for relay 200 includes control conductor 220 oi the trunk. wiper ll of intermediate selector 18, contacts 00, trunk conductor 8S, wiper 60 oi transmission selector TB, contacts 55, and ground at contacts 22. Relay 206 operates, completes a locking circuit for itself at contacts 249, prepares a new circuit for relay 208 at its lower contacts, and prepares a circuit for the supervisory lamp Li at contacts 218.

Shortly after the last impulse oi the series relay 201 restores and opens the holding circuit 01' relay 200. Relay 208 restores and prepares the rotary magnet circuit at contacts 2". The operator now dials the fourth digit of the called number and the impulses are repeated as before to relay 203. Each time relay 202 restores an impulse is transmitted over the previously traced impulse circuit which has now been extended by way of contacts 250, 250, and 282 to rotary magnet RM. Relay 201 again energizes and remains energized throughout the series of impulses and at this time completes a circuit by way of contacts 250 and 258, resistance 20!, upper winding of marginal and diil'erential relay 2 to battery. Relay 2 when energized over its upper winding in series with resistance 20! energizes only partially and closes contacts 219 which are designated by the Roman numeral 1. The closure of these latter contacts prepares a circuit for operating the relay fully upon the release of relay 201 as will be explained subsequently. The rotary magnet responds to the impulses transmitted by relay 203 and rotates the wiper step-by-step to the bank position in which the contacts of the called line are accessible.

Shortly after the last impulse of the series transmitted to the rotary magnet, relay 201 will restore and complete the circuit for energizing relay 2| I in its second step. This relay upon energizing completely locks by way of contacts 219 and 218 and vertical off-normal contacts H5. The lmpulsing circuit previously traced to the rotary magnet is switched over at contacts 28l to two-step relay 209. The lower set of wipers, that is, wipers 2fl1289, are connected up at contacts 215, 211, and 203. Further, a circuit is prepared for the lower winding of relay 2" at contacts 280. The connector is provided with two separate sets of wipers and two diilerent lines are accessible in each bank position. The particular one of these lines to be selected will depend upon the last digit dialled by the calling operator. The final digit of the number may be either the digit 1 or the digit 2, depending on the set of wipers required. Assume first that the digit i is dialled and repeated by the transmission selector to relay 202. Relay 203 on releasing completes a circuit from ground, contacts 238 and 0, lower contacts of relay 205, contacts 212, 260, 266, and 28L lower winding of relay 209 to battery. Relay M! operates only in its first step, thereby preparing a circuit for both windings in series at contacts I. At the termlmidcn of the impulse, relay 2|! operates and removes ground from the impulse circuit and relay ill operates in its second step over its two windings in series. The original operating circuit of relay 2 is opened at the upper contacts of relay 2", a point in the test circuit is closed at contacts 283, and the impulse circuit is transferred by way of contacts 2|! and "I to the lower winding 01' relay 2. In case no further impulses are transmitted. as will be the case in the present instance. the connector will test over the lower test wiper as will be explained subsequently.

In case the last digit of the number had been the digit 2, a second impulse would be transmitted over the impulse circuit to energme the lower winding 01' relay 2. The two windings of this relay are differentially wound, that is. they oppose each other and consequently the result of the second impulse is to restore relay 2 to normal position. The relay on releasing opens the circuits of both of its windings and remains normal regardless of any subsequent impulses which may be transmitted. The set of wipers comprising wipers 2. 2. and 2 is connected up and the test proceeds in the same manner as over the other set oi wipers.

Relay 2|! energizes during the transmission of the last impulse or series oi impulses as previously explained and prepares the test circuit. After the dialling oi the final digit and before the release of relay 2|! which is slow releasing. test relay 2|! is connected by way of resistance 2. contacts 252 and 2, upper winding of relay 2lll, and either of contacts 2'" or 21"! to test wiper 2" or 28!. Assuming that the called line is busy when the connection is extended there will be ground on the test contact encountered by the active test wiper and relay 205 will partially energize. Under these conditions relay 205 closes only contacts 2.5, thereby preparing a circuit for operating the relay fully upon the release of relay 2". The resistance of relay 2! is such that relay 2", is not operated. When relay 2|! restores alter a slight delay. a circuit is completed by way oi contacts 245, 243, and 253 for operating relay 1|! fully and the relay locks by way of contacts 2" and 2. to ground at contacts 219. The busy signalling circuit is closed at the upper contacts of the relay. a circuit is completed at contacts 242 for relay 2, and the impulsing circuit is opened at the lower contacts of the relay. Relay 2|] operates, disconnects relay 2|! from the control loop at contacts 222 and 229 and connects the loop through to the talking conductors of the connectgr at contacts 223 and 22!. Battery iced relay 2" is disconnected from the talking condoctors of the switch at contacts 22 and 221. A circuit is prepared for relay 2 and the lower winding of the relay 2|! at contacts 225 and the local holding circuit of relay 2 is opened at contacts 226.

The disconnection of relay 2|: from the control loop opens the holding circuit of the relay 5 of transmission selector Ts and that relay restores. Relay 5 completes an obvious circuit for relay 6 which operates and by opening contacts 2i and 2| and closing contacts 2| and 2! reverses the battery and ground connections to the incoming trunk by reversing the connection of relay H with respect to the trunk conductor.

Relay 6 disconnects the upper winding of relay 7 i from the control loop and connects the two windings or battery-iced relay 1 thereto. Reten-ing now to the connector, ground is intermittcntly applied to the upper talking conductor by way or the busy tone interrupter, contools 2", upper contacts of relay 2|, contacts 223, conductor Ill, wiper of switch 18, contacts 8|. conductor a, wiper SI of switch T8. upper contacts of relays I4 and II,

contacts 2|, upper winding of relay I to battery. Relay 1 operates intermittently and on each operation completes an obvious circuit for relay 8. intermittently to disconnectrelayiliromtheincomingtrunkbyopening contacts 2| and 3|. The release of the connection is prevented by the closure of a holding circuit across the two windings of relay II by way of contacts ll of relay 8. In the operator's cord circuit polarised relay i operates in response to the reversal of battery which takes place upon the operation of relay 6. The intermittent disconnection of relay II from the trunk conductors causes the polarized relay to enersize and deenergise and thereby light the supervisory lamp intermittently. This gives the calling operator a distinctive vis al signal indicating that the called line is busy. The operator is then expected to release the connection as will be explained subsequently.

Assuming that the called line is idle when a connection is extended thereto as described above. the following operations take place. An idle line is characterised by the presence of battery potentialon the test contact, the battery being normally connected thereto through thewindingoithecut-oflrelayofthelineswitch. After the test circuit including busytestrelayaiwillbecompletedasbeiore described. The test relay does not operate due to the battery potential encountered by the test wiper. when relay 2|! restores shortly after thelastimpulseoitheserieathetestclrcuitis switched from battery through relay 2|| to ground at contacts 2, and relay 2" operates in serieswiththecut-oirrclayottbesubscriber's ,lineswitch. Relay 2" completes the ring-backtone circuit at its upper contacts, prepares the ringing circuit at contacts 2|? and its lower contacts, completes a circuit for relay 2ll at contacts 268, prepares the circuit for supervisory lamp Ll at contacts 2, applies ground directly to the test wiper at contacts 2", completes a locldng circuit for itself at contacts 2'", opens the impulsing circuit at contacts 212, and completes the circuit oi! relay 2" at contents 2". Relay 2" operates to connect the lower winding 01' relay "2 and relay 2" in series and to disconnect relay 2|! from the line aswasdcscribedioracalltoabusyline. Relay operates and opens the ringing circuit at contacts 2" and 2|2, thereby placing the signalling of the called subscriber under control of the calling operator. 'Ihe disconnection of relay 2 from the trunk permits relay I of battery over the incomingtoll trunk. Polarized relay l oi the cord circuit operates and closes the circuit oi the mpervisory lamp at the switchboard to give the calling operator "line seizure mpervlsicn.

when the operator desires to Signal the called subscriber key R .will be operated to the left. thereby applying ringing current to the toll trunk to operate relay which is bridged across the trunk conductors in series with a condenser. Relay 0 completes an obvious circuit for relay II which operates, completes a holding circuit for relay Ii at contacts 34, and removes ground from the control conductor by opening contacts 28. Removal oi ground from the control conductor permits relay 200 of the connector to restore and open the circuit 0! relay 200. Relay 200 releases and completes the ringing circuit which may be traced from the generator or battery, interrupter contacts, upper winding of ring-cut-ofl relay 206, contacts 254 and 281, and either contacts 214 or 215 and the associated wiper 280 or 208, depending on the wiper set used, llne conductor 292 through the bell and condenser at the called substation, line conductor 20l, wiper 201 or 290 of the connector. contacts 283 or 204, lower contacts of relay M0 and contacts 262 to ground. The bell at the called substation rings intermittently.

When the called subscriber answers a direct current bridge is closed at the substation and relay 200 operates. Relay 206 locks to ground on the control conductor which is grounded as soon as the operator restores the ringing key. Relay 206 also completes the circuit of relay 200 which operates to open the ringing circuit and contacts 254 and 262 and complete the con nection between the control loop and the called subscriber's line at contacts 250 and 20L Relay 1 of selector TS operates over the called subscribers loop and completes the circuit of relay 0. Relay 0 operates, disconnects relay H from the toll trunk, and completes a local circuit for maintaining the relay operated. The disconnection of relay H from the trunk permits relay I of the cord circuit to restore and extinguish the supervisory lamp, thereby giving the operator "answering" supervision. The operator may then switch the calling party into the connection in the usual way and disconnect her own telephone set therefrom.

When the called subscriber hangs up at the termination of the call, relays l and 0 restore and relay II is again connected to the toll trunk. Relay l of the cord reoperates and completes the circuit of the supervisory lamp to give the usual disconnect" supervision. The operator may then release the switches involved in the connection by withdrawing the plug from the jack.

Release The called subscriber controls the release of the connection, that is, the operator is not able to release the same by withdrawing the plug of the calling cord from the jack until the subscriber hangs up. This is due to the fact that the called subscriber maintains relays I and 0 energized. Relay 0 maintains the holding circuit for relay II which in turn maintains the circuit of relay I2 and prevents the switches from releasing.

When the called subscriber hangs up at the termination of a call, relay 1 releases and opens the circuit of relay 8. Relay 8 releases and reconnects relay H to the trunk, thereby placing the latter relay under control of the calling operator. The operator may then release the connection by withdrawing the plug of the calling cord from the jack. The circuit of relay H is opened and the relay restores and opens the circuit of relay l2. Relay i2 restores and completes the circuit of the release magnet RLM by way of contacts H, 43, iii, and the vertical oil-normal contacts. The release magnet restores the switch wipers to normal position in the usual manner. The opening of contacts 44 and 40 upon the release oi relay i2 permits relay H to restore. The return of the switch wipers to normal position results in the operation of the'various vertical off-normal spring contacts. Contacts I! open the circuit of relay 0 which restores and contacts l0 reconnect the upper winding of relay [I to the trunk line.

The removal of ground from release-trunk conductor 04 due to the release of switch TS permits relay 15 of selector 18 to restore and complete the circuit of release magnet RLM. The release magnet restores the switch wipers to normal position in the usual manner and upon their return thereto the release magnet circuit is opened at off-normal contacts 08. The closure of oiT-normal contacts 00 reconnects the upper winding of relay 14 to the release-trunk conductor.

The removal of ground i'rom release-trunk conductor 2lil upon the release of the preceding switches permits relay 20! to restore and open the circuit of relays 202 and 204 at contacts 225. These relays accordingly restore and at their lower contacts complete a circuit for release magnet RLM by way of off-normal contacts 213. Relay 204 removes ground from the local holding circuit, thereby permitting relay 2l0 to restore. The removal of ground from the control conductor, upon the release of the switch TS, permits relay 206 to restore. When the switch wipers reach normal position the various off-normal contacts operate, contacts 2|3 open the release magnet circuit and contacts 2l5 open the holding circuit of relays 205 and 2i I. The switches are thus returned to normal position and are in readiness to respond to the next call.

Supervisory signals Returning now to the point in the connection at which connector C connects with the called line, the operation of relay 20l, as stated, disconnects impulse relay 203 from the trunk conductors and connects relay 204 in series with the lower winding of relay 202. Relay 203 restores and at contacts 231 opens the original energizing circuit of relay 204. Relay 204 is now energized in series with the lower winding of relay 202 and ground at its own upper contacts. Relay 204 maintains the holding circuit of relay 2H] and maintains ground on release trunk conductor 290 to mark the connector busy to local selectors. In addition to the foregoing, relay 204 maintains one open point in the circult of the supervisory lamp L2 at contacts 24I to prevent the lamp from lighting to give a false supervisory signal. Relay 202 maintains an open point in the circuit of supervisory lamp Ll at contacts 230 to prevent that lamp irom lighting and giving a false supervisory signal. In local connections, relay 204 is released and relay 202 remains operated when the calling subscriber hangs up first. This results in the closure of the circuit of lamp L2. The called party on hanging up first releases relay 202 while relay 204 remains operated and completes the circuit of lamp Ll.

Toll call to a party line The operations involved in extending a toll call to a party line will be described in connection with a call to substations Ti and T2 (Fig. 3). The operator connects the calling end of a cord with a trunk extending to an idle toll transmission selector for example, the selector TS and dials the first two digits of the number with exactly the same results as described for the previous connection. In this case, however, the intermediate selector will be operated to a level in which trunks extending to the party-line connector are accessible. It may be assumed that the trunk comprising conductors Iii-Ill is the trunk selected. Ground is extended over release trunk conductor Ill and control conductor Ill as in the previous case, and the control loop is extended over talldng conductors Ill and III as before. The ground on the release trunk conductor by way of the busy key contacts and the vertical oil-normal contacts operates relay Ill. Relay Ill prepares a holding circuit for itself at contacts 365, completes the impulsing circuit to vertical magnet VM at contacts Ill, and opens a point in the circuit of ring-cut-oif relay Ill at contacts Ill. The ground on the release trunk also permits impulse relay Ill to operate over the calling loop and complete an obvious circuit for relay Ill. Relay Ill operates and supplies ground to the local holding circuit at its upper contacts, applies ground directly to the lower winding of relay Ill at contacts III,

prepares the impulsing circuit at contacts Ill.

and opens the release magnet circuit at its lower contacts. The dialled impulses are repeated by the toll transmission selector in the usual way and relay Ill follows the impulses and repeats them by way of its lower contacts, contacts III, lower contacts of relay I05, contacts Ill, Ill, and 366, winding of vertical magnet to battery. The vertical magnet raises the wipers step-bystep to the called level. Relay I06 which is connected in parallel with the vertical agnet operates on the first impulse and, due to its slowreleasing characteristics, remains operated throughout the series of impulses. The off-normal springs operate on the first step of the wipers and among other things, open the original energizing circuit of relay Ill. Relay Ill, however, remains operated throughout the series of impulses over a circuit including contacts lit, 36 l, and I42 to ground on the local holding conductor.

Shortly after the last impulse of the series, relay I06 releases, opens the previously completed holding circuit of relay Ill and completes a circuit for relay Ill and the upper winding of relay 309 in series by way of contacts II and Ill. Re-

lay 3 I ll remains energized and relay Ill energizes in this circuit, the latter relay transferring the previously traced impulse circuit to rotary magnet RM by way of contacts 362.

The operator now transmits the fourth series of impulses which are repeated by the transmission selector to impulse relay Ill. Relay Ill repeats the impulses to rotary magnet RM which rotates the wipers of the switch step-by-step to the contact position in which the called line is accessible. Relay I86 operates in parallel with the rotary magnet, opens the circuit over which relays Ill and Ill were being held operated at contacts Ill, and completes a holding circuit for the lower winding of relay Ill alone at contacts 342. Relay Ill restores and prepares the circuit of the stepping magnet SM of the auxiliary switch. Relay Ill remains energised throughout the series of impulses. The release of relay Ill completes an operating circuit for relay Ill, contact and wiper Ill relay Ill from the grounded control ot inductor and contacts Ill and Ill. Relay Ill completes an obvious locking circuit for itself, opens a point in the circuit over which relays Ill and s 7 III were previously energmed, and opens the ringing circuit.

Shortly after the last impulse of the series, relay Ill restores and opens the holding circuit of the lower winding of relay Ill. Relay Ill restores and transfers the impillsing circuit by way of contacts I and Ill to stepping magnet $11 of the auxiliary switch. The value of the final digit of the number will depend both upon theparticularoneotthetwolinesaccessiblein the bank pofltion to which the switch wipers have been set and on the particular party of the called line with which a connection is desired. Fbr example the party 1 on the line accessible to the upper set of wipers will be called by the digit 1 while the party 1 on the line accessible to the lower set of wipers will be called by the digit 6. It will be assumed in the present case that the digit 2 is dialled, indicating a call for the subscriber at station T2. The impulses are repeated as in the previous instances and stepping magnet 8M advances wipers Ill and ll! of the auxiliary switch to the second set of contacts in the switch banks. Relay Ill operates in parallel with the stepping magnet and prepares the test circuit at contacts Ill. At the end of the series of impulses and before relay Ili has had time to restore, the called line is tested for its busy or idle condition over a circuit which may be traced from test wiper Ill, upper windingoi oi the auxiliary switch. contacts Ill, resistance Ill, winding of relay Ill to battery. In case the called line is busy there will be a ground on the test contact and relay Ill will operate in its first step closing only contacts Ill. When relay Ill releases after a slight delay, a circuit will be completed independent of resistance III to operate relay Ill completely. Relay Ill closes the busy signalling circuit at its upper contacts, completes a circuit for relay Ill at contacts Ill, completes its own locking circuit at contacts Ill, and opens the impulsing circuit of its lower contacts. The callingoperatorisgivenabusysisnalduetothe intermittent connection of ground to the upper trunk conductor by way of contacts Ill, upper contacm of relay Ill and contacts 323.

Incasethelastdigitof thenumberls'l for example, instead of 2, as explained previously, the test circuit will be completed over the seventh contact engaged by wiper Ill, the upper winding of relay Ill and test wiper Ill. The operation of the busy relay Ill will be exactly the same as in the prior connection in case the line is busy.

In the case of a call to an relay does not operate in either of the test circuits previously described, and, when relay Ill releases shortly after the last impulse of the series, a circuit is completed for the upper winding of the switch through relay III or III. In case relay II! is included in the circuit as will be the case tor-a number ending in the digit 2. this relay operates and completes the ring-back-tone circuit at its upper contacts, connects up wipers Ill and Ill at contacts Ill and its lower contacts, completes a circuit for relay Ill at contacts Ill, prepares the circuit for lamp Ll at contacts lll, completes the pick-up circuit at contacts Ill, applies direct ground to the test wiper at conidle line, the test tacts 31!; completes a locking circuit for itself at contacts 88., and opens the lmpulsini circuit at contacts ill. a

At this point it may be noted that the pick-up circuit above-mentioned is provided to control the start of ringing. In case the 111 81118 used for signalling purposes is of the so-called code type, that is, consists of various codes or ringing current or a single frequency, it is necessary to prevent ringing current from being applied to the line until the interrupter is at the beginning 01 a code. This arrangement is well-known and pick-up conductor III in this case would be connected to the pick-up conductor of the code interrupter. In the case of a toll call, however, the pick-up circuit is not effective since it is open at contacts 382. Accordingly, no ringing will take place until the operator exchanges the usual ringing control and the code interrupter is in the proper position.

In the case of a system using harmonic'ringing, that is, a diflerent frequency for signalling each of the parties on the line, the pick-up circuit above described is not necessary. Relay llii must be operated, however, and in this case the contact spring of relay 3|! is connected directly to ground instead of to the pick-up conductor "8. This arrangement makes it possible to use the same connector for either code or harmonic ringing with a very simple change consisting of the switching of the connection to one spring of relay III.

Assuming that the last digit of the called number was the digit 7, the following operation is had in case the called line is idle. The test circuit, as previously explained, will include the seventh contact of wiper 392 of the auxiliary switch, upper winding of relay 3 and test wiper 383. When the line is idle, relay 805 does not operate and after relay 30B releases the circuit is completed for operating relay 3. Relay 3H connects up line wipers 385 and 381 at contacts 369 and 31!, applies ground directly to test wiper 383 at contacts 310, and completes a locking circuit for itself and an energizing circuit for relay 3|! at contacts 3". Relay 3l2, accordingly, operates and closes the various circuits described for its operation in the previous instance.

Upon the connector establishing a connection with a called line, as described in any of the above instances, a circuit is completed for relay IM and that relay operates to disconnect impulse relay 303 from the trunk and to shortcircuit the talking condenser of the switch.

The lower winding of relay 302 is connected in series with relay 3 at contacts 325. The disconnection of the impulse relay of the trunk permits the restoration of supervisory relay 5 of the transmission selector and line seizure supervision is returned to the calling operator in the usual way. Relay 303 of the connector restores and opens the original energizing circuit of relay 3. Relay 3M remains energized in series with the lower winding'of relay I02 and the latter relay also operates. Relay. 3" maintains ground on the various holding circuits and maintains an open point in the circuit of supervisory lamp L2 to prevent a false supervisory signal. Relay 3M opens a point in the circuit of supervisory lamp LI to prevent this lamp from giving a false supervisory signal.

The calling operator initiates the ringing, as previously explained, by removing ground from thecontmlconductoratthetnmnissionselectonwhichpernntsrelaylll oi'theoonnector to restore. Relay lIl completes the pick-up circuitatcontectslllandnelaylll operatesat themopertimetocompleictherin lnscircuit. Rinflng current is now applied from the selected generator lead "-88, wiper "I of the aunlliaryswimamlinthecaseofanodddiglt, over the resistance, lower contacts of relays III, I", and Ill, contacts I'll or th lower contacts ofrelays Ill and ill, wiper III or I, over one sidsoithecailediinethroughthebell andoondenser at the substation, back over the other side oi the lines and either wiper III or II, contacts I" or the upper contactsoirelay Ill and contacts 314, contacts 8 and I", and upperwinding of relay III to battery. In case the last digit of the called number is an even digit, the ringing current will be applied over the lower contacts of relay fill, contacts I", winding of relay 308 to battery. This ringing current on which ground is superimposed energizes relay "I. Relay Illl locks to ground on the local holding conductor and transfers the ringing circuit by way of contacts 151, resistance, lower contacts of relay Ilil, contacts 858 and I, and by way of contacts 389 or the upper contacts oi relay 3H and contacts 314 to wiper 38! or "I of the connector and thence over the called line. The return circuit for the ringing current includes one of the lower wipers of the connector, lower contacts of relays 3H and III or contacts 313, lower contacts of relay I01, contacts 15!, upper winding of relay III! to battery. It will thus be seen that the positionmg of the auxiliary switch accomplishes four different functions, namely the selection of the particular ringing current to be used, the selection of the set of wipers to be used, the selection of the side of the line to which the ringing current is to be applied, and the closure of the circuit of one or the other of the switch through relays.

When the called subscriber answers a direct current bridge is closed at the called substation and relay 301 operates. Relay 30! opens the ringing circuit at contacts 346 and its lower contacts, and extends the calling loop through by way of contacts I" and $54 to the batteryfeed bridge at the transmission selector. The battery-feed relay operates as previously described and gives the operator Answering supervision.

The release of the connection is the same as for the previously described connection to an individual and is initiated by th called suhscriber restoring his receiver and the operator withdrawing the plug of the calling cord from the jack. The removal of ground from the release trunk and holding conductors permits relays 3M and 301 to restore. Relay till opens the circuit of relays 302 and IN and these relays restore. Relay 3M opens the circuit or relays 308 and 3M and the latter opens the circuit of relay M2 and these relays restore. The circuits for release magnet RIM oi the connector and release magnet ARM of the auxiliary switch are closed by way of the lower contacts of th relays and 8M and the respective oil-normal contacts. These magnets restore the wipers to normal position in the usual manner, and the switches are ready to respond to the next call.

Local calls The operation of the connector switches in local calls is generally the same as in toll calls except for the diil'erences to be pointed out hereinafter. When a connection is extended to connector C (Fig. 2). for example, by a local selector which has acces thereto over the trunk conductors 201-200 the connector opcrates as follows: Ground is fed ahead over release trunk conductor 20! and energizes relay 2". This ground also permits relay 203 to operate over the calling loop and complete a circult for relay 204. Relay 200 returns the ground on the release trunk conductor to hold up the preceding switches and this ground by way of the contacts of the busy key BK and the vet-ti cal oil-normal contacts marks the connector busy tothe toll selectors.

The response the switch to the dialled impulses is exactly the some as for a toll connectlon and will not be described in detail. It should be noted, however, that relay III is not operated during the vertical movement of the switch since there is no circuit over control conductor 220, On the first vertical step of the wipers oil-normal contacts 2!! separate toll release trunk conductor M0 from local release conductor 200. The connector is still busy as far as the toll selectors are concerned since iow impedance relay 200 and its battery connection has been disconnected and the switching relays of the toll selector are unable to operate and stop a selector on the trunk leading to this switch.

The called line is tested in the same manner as for a toll call and if the line is busy relay 2" operates and locks and connects the busy tone to the upper talking conductor by way of contacts 206 and the upper contacts of relay 200. Since the toil and local release trunk conductors have been separated, as above described, and since there is no ground connection to conductor Ill, there will be no circuit for relay Ill and, accordingly, that relay does not operate as it did in a toll connection. Impulse relay 202 remains operated over the loop of the calling lin and maintains the connector in operated condition. In the meantime the subscriber is given the busy tone to indicate that a connection with the wanted line is imposmble, and the subscriber is expected to hang up and release the connection.

In case the called lin is idle when a connection is extended thereto, relay 20| operates, as previously explained for a toll connection, and wmpletes the ringing circuit since relay 200 will be normal. The ringing current is intermittently transmitted over the line immediately after its seizure and with no further control from the calling subscriber. when the called subscriber answers. reiay 206 operates over the called subscnibe'r's loop and at its lower contacts completes a circuit for relay 200. Relay 208 operates and opens the ringing circuit at contacts 204 and 202 and at contacts 250 and 2 extends the called line through to battery-teed relay 202. Relay 202 operates and reverses the connection of relay 203 with respect to the trunk conductors. Relay 202 also opens the circuit of supervisory lamp Ll, closes a point in the circuit of supervisory lamrp L2 and opens a point in the circuit of the release magnet.

At the termination of a call, one or both of the subscribers hang up and in the latter case the entire connection is released, In case the called subscriber hangs up first, relay 202 restores and at contacts 230 completes a circuit for supervisory lamp Ll. Relay 203, however, remains energized over the calling line and prevents the release of the connector.

Lamp Ll glows to notify the exchange attendant that a connector is being held by a calling subscriber after the called subscriber has hung up. When the calling subscriber finally hangs up, relay 20! releases and opens the circuit of relay 204. Relay 204 removes ground from the release trunk conductor and from the local holding conductor and closes the circuit of the release magnet. The release magnet operates to restore the switch wipers to normal in the usual manner and the various relays of the connector restore to normal.

In case the calling subscriber hangs up first, relays 200 and 204 will release and relay 202 will remain energized over the loop of the called subscriber, Relay 200 removes ground from the local holding circuit and from the release-trunk conductor of the local trunk, Relay 202 maintains the ground on the local holding circuit and its own lower winding by way of contacts 200, 200, and 2. In addition, relay 202 opens the circuit of lamp Ll at contacts 230, closes the circuit of supervisory lamp L2 at contacts 230, and opens a point in the circuit of the release magnet. The removal of ground from the local release trunk conductor permits the preceding switches to release. The local trunk, however, cannot be seized in a new connection, due to the fact that relay 200 and its associated battery is not connected to the trunk, as off-normal contacts 2 are open. Lamp L2 glows to notify the exchange attendant that a connector is being held by acalied subscriber who has failed to hang up after the calling subscriber has withdrawn from the connection. When the called subscriber finally hangs up, relay 202 releases and opens the holding circuit of the various operated relays and completes the circuit of the release magnet. The release magnet operates to restore the switch wipers to normal position in the usual manner.

It may be noted that during a connection with either a busy line or an idle line, relay 20! will be connected to test conductor 2|! of the toll trunk. Relay "I is a high-resistance relay and does not energize the test relay of a selector sufllciently to stop a switch on the trunk and, consequently. toll selectors will pass over this trunk, Relay 20l is somewhat slow to operate and the momentary application of ground to conductor 2", as a toll selector tests the trunk, does not operate the relay, However, a slight operation will be of no consequence since the selector will immediately pass by the trunk and restore the relay to normal condition.

The extension of a local connection over connector Cl (Fig. 3) is exactly the same as for a toll connection except for the diil'erences due to the absence of ground on the toll-test and control conductors. These differences were fully explained in connection with the individual line connector and need not be repeated. It is sulficient ,to note that relay 301 does not operate until the called subscriber answers and that relay 201 does not operate at any time during the connection. Relay 303 feeds talking battery to the calling subscriber, relay I02 feeds talking battery to the called subscriber. These two battery-feed relays Jointly control the release of the connector. The release is exactly the same as described for the connector C.

All-trunks busy metering In the preceding examples it is assumed in each case that the selector found an idle trunk in the called group. The operation resulting from the failure to find an idle trunk will now be described, Assuming first that selector T8 (Fig. 1) has been operated to a level in which all trunks are busy, the selector will rotate, as described in previous connections. In this case since no idle trunks are available, the wipers will be stepped to the eleventh position. A set of contacts are provided in this position to which no trunk is connected. The contact accessible to the lower wiper, however, is connected to an overflow or all-trunks busy meter. When the wiper reaches the eleventh position the eleventh-position cam contact designated RC operates with the results that the circuit of relay 5 is opened and the interrupter INT is connected to the upper talking conductor of the switch. Relay 5 restores and completes a circuit for relay 6. Relay Ii reverses a battery and ground connections to the toll-trunk and connects up battery-feed relay 1. The ground intermittently applied to the upper talking conductor of the switch by the interrupter operates relay 1 intermittently and this relay operates relay 8 which periodically opens the trunk as explained for attempted toll calls to busy lines. 25 The supervisory lamp at the operators position is flashed to give the all-trunk busy signal. A further result of the operation of the elevenposition cam contact is the connection oi the upper winding of relay 13 in parallel with release relay l2 and relay It operates. After noting the busy signal the operator will release the connection by withdrawing the plug P from the jack J thereby opening the circuit of relay ll. Relay ll opens the circuit of relays l2 and 35 I3 and a new circuit is closed for the lower winding of relay l3 over contacts ll, 42, and 0. Relay l2 restores after a slight delay and opens the second circuit of relay l3 which relay, however, remains operated for a short interval after the release of relay l2. During this interval ground is applied by way of contacts ll, 43, and 50, wiper 6|, contacts 61, through the winding of meter 68 to battery. The meter operates to register the attempted call to a group in which all trunks are busy. The meter incidentally may serve a number of groups or may be individual to one particular group, the operation in any case being as described. When relay i3 finally restores, a circuit for the release magnet RLM is completed and the magnet returns the switch wipers to normal position.

The operations resulting from intermediate selector IS encountering a group in which all trunks are busy is substantially the same as that described for the transmission selector. In this case a circuit is completed through the upper winding of relay TI to the grounded release trunk conductor. Upon the opening of the control loop from the transmission selector which takes place when the operator disconnects the calling plug from the trunk, relays l2 and i3 restore. During the time required for relay T3 to restore a new circuit is completed for the lower winding of relay ll which accordingly remains energized a short time after relay l3 restores. Upon the restoration of relay 13 a metering circuit is completed by way of contacts 89, I1, 19, 8|, wiper 86 and the eleventhposition contact engaged thereby, to the meter connected to the contact, which will correspond to the meter shown in connection with the transmission selector. Relay i4 restores after a short interval and completes the circuit for the 75 release magnet RIM which returns the selector to normal in the usual manner.

Whatisclaimed is:

1. In an automatic switch having access to a plurality oi groups of trunks, a switching relay having a polarizing winding and an operating winding, means for energizing said operating winding responsive to the switch being taken into use to prepare the relay for operation, means responsive to directive control for pcsitioning the switch in selective relation with any one of said trunk groups, means for automatically operating the switch to hunt over the trunks oi a selected group, means for energizing said operating. winding to operate the relay responsive to the switch finding an idle trunk in the group hunted over, and means controlled by said relay for interrupting the automatic operation and for effecting the seizure of the idle trunk.

2. An automatic switch as claimed in claim 1 in which the switching relay on operating disables its operating winding and completes a circuit for maintaining itself operated over its polarizing winding.

3. An automatic switch as claimed in claim 1 in which a test wiper is connected to the operating winding 01 the switching relay during the automatic hunting operation and in which the connection of the test wiper is transferred to the polarizing winding of the switching relay upon the operation of the relay.

4. In a telephone system, a selector switch, a test wiper for the switch, test contacts accessible to the wiper, said contacts being characterized under diirerent conditions by a connection to battery through a low resistance, a connection to battery through a high resistance, a connection to ground, or the absence of potential, a polarized relay for the switch, means for operating the switch to cause said wiper to engage said contacts successively, mean responsive only to the wiper engaging a contact to which battery is connected through a low resistance for operating said relay, and means controlled by said relay for stopping the switch.

5. In a telephone system, an automatic switch, a trunk including two talking conductors and a test conductor terminating in the switch, a double-wound changeover relay for the switch, primary and secondary magnets for the switch, means for extending a connection to the switch via said trunk, means responsive to said connection for operating said relay over a circuit including one winding of the relay and said test conductor, means controlled by said relay when operated for connecting up the primary magnet, means controlled over the talking conductors of the trunk for operating said primary magnet to set the switch, means for opening the operating circuit of said relay at the beginning of the primary operation of the switch, means for completing a holding circuit including the other winding of the relay during the primary operation 01 the switch, means for opening said holding circuit to release the relay upon the completion of said primary movement, and means controlled by said relay on releasing for disconnecting the primary magnet and for connecting up the secondary magnet.

6. In a telephone system, a toll selector, talk- 'ing and test wipers for the selector, a line relay,

a release relay and a changeover relay for the selector, means for operating said relays responsive to the seizure of the selector, a group of trunks, means for operating the selector into selective relation with the trunk group, means for releasing said changeover relay to cause the selector to hunt for an idle trunk in the group, means responsive to the failure 01 the selector to find an idle trunk in the group for re-operating said changeover relay and for extending a connection via one of said talking wipers, means for releasing said relays in succession, means responsive to the release of the line and release relays for closing a circuit over said connection, and means responsive to the release of said changeover relay for opening said circuit and for releasing the selector.

'7. A telephone system as claimed in claim 6 in which the changeover relay is reoperated due to the closure of contacts adapted to be closed mechanically when the wipers of the selector are moved beyond the position in which the last trunk of a group is accessible.

8. In an automatic switch, incoming conductors including two talking conductors and a test conductor, a double wound line relay, circuit connections connecting a source of current and one winding of the relay in series to one of said talking conductors, and other circuit connections connecting the other winding in bridge of the other of said talking conductors and said test conductor.

9. An automatic switch as claimed in claim 8 in which the connection between the relay winding and the test conductor is opened when the switch is caused to leave its normal position.

10. An automatic switch as claimed in claim 8 in which the circuit connections between the relay windings and the two talking conductors include reversing contacts of a second relay.

11. In a telephone system, lines, an automatic switch, means for operating the switch to connect with a desired one 01 said lines, a test wiper for the switch, test and switching relays in the switch adapted, respectively, to give a calling party a busy signal and to complete a connection to a line, and means for temporarily connecting the wiper and said relays in series to render the relays effective.

12. In an automatic switch, means for respending to a plurality of series of impulses to select a called line, talking and test wipers, a test relay for determining the idle or busy condition of a call line, a switching relay for conmeeting up the talking wipers to complete a connection to an idle called line, and means responsive to the last series of impulses received by the switch for temporarily connecting said test wiper and said relays in series.

13. An automatic switch as claimed in claim 12 in which the series connection of the test wiper and the two relays is completed immediately after the first impulse of the last impulse series and is maintained for an interval after the last impulse of the series whose length is dependent upon the releasing time of a slowreleasing relay.

14. In a telephone system, a connector switch, means for extending connections of two classes over the switch, a release relay and a batteryfeed relay for the switch, supervisory si nals, means for energizing and deenergizing said relays in separate circuit to control said signals in connections of one class, and means for energizing said relays in the same circuit to disable said signals in connections of the other class.

15. In an automatic switch, two sets of wipers, a double wound difierential relay, means for setting the switch, means for operating said relay over one winding to connect up one set of wipers responsive to the completion of the setting of the switch, and means controlled at will tor energizing the other winding oi said relay to restore the same and connect up the other set of wipers.

16. In an automatic switch equipped with two sets 01' wipers and adapted to respond to three series of impulses, anormally open test circuit adapted to operate with either set of wipers, two relays, means for positioning the wipers responsive to the first two series of. impulses received, means for operating one 0! said relays to render one set of wipers eiiective responsive to the completion oi the second series of impulses, means for operating the other oi said relays to complete said test circuit responsive to the first impulse of the third series. and means for deenergizing said one relay to render the other set 01 wipers eflective responsive to the second impulse of the third series.

17. In an automatic switch equipped with two sets oi. wipers, a wiper switching relay. a second relay, an impulsing circuit, an operating magnet connected to said circuit, means for operating said first relay to switch wipers and to switch the impulsing circuit irom said magnet to said second relay, means for operating said second relay over said impulsing circuit, and means controlled by said second relay for switching the impulsing circuit from itself to said first relay;

18. In an automatic switch equipped with two sets of wipers, means for responding to two series of impulses to set the wipers on contacts of two diflerent lines, means for responding to a third series of impulses to select a set of wipers, and means for rendering the switch eflective for testing for the busy or idle condition of a line immediately after one impulse of the third series has been received.

19. In a telephone system, a connector switch and an associated auxiliary switch, primary and l secondary magnets for the connector, a stepping magnet for the auxiliary switch, two changeover relays, means for operating the iirst relay responsive to the seizure of the connector, circuit connections controlled by the first relay for connecting up said primary magnet, means for operating the primary magnet to partially set the connector, means for operating both relays in series responsive to the completion oi said partial setting, circuit connections controlled by the second relay for connecting up said secondary magnet, means for operating the secondary magnet to complete the setting of the connector, means for releasing both or said relays responsive to the completion of the setting or the connector, and circuit connections controlled by said relays jointly for connecting up said stepping magnet.

20. In a telephone system, a connector having a plurality 01 sets 01' wipers. a switching relay ior each set of wipers, lines accessible to said wipers, an auxiliary switch individual to said wipers, a plurality oi sources or ringing current, means for operating the connector to position the wipers on certain oi said lines, means for thereafter operating said auxiliary switch, and means controlled by said auxiliary switch for selecting a particular one oi said current sources, for determining the side of the line to which the selected current source is to be connected, and for rendering only one or said switching relays operative to test the line engaged by its associated set of wipers.

21. In a telephone system, a selector switch having a fixed contact set and a movable contact set adapted to engage said fixed contact set, each of said contact sets including two line contacts and a control contact; a line including two line conductors and a control conductor terminating at the respective contacts in said fixed contact set; another selector switch connected to said line and including a relay operative to initiate operation of said other selector switch; an operating circuit for said relay including one terminal of a source of supply derived in said other selector switch, a winding of said relay, one of said line conductors. one of said fixed line contacts, a loop extending between said movable line contacts, the other of said fixed line contacts, the other of said line conductors, a connection extending between said other line conductor and said control conductor, said control conductor, said fixed control contact, said mov able control contact, and the other terminal of the source of supply derived in said first-mentioned selector switch, whereby no potential difference is present between said fixed line contacts when said other selector switch occupies an idle position; and means for causing said movable contact set to engage said fixed contact set, thereby to complete said operating circuit.

22. In a telephone system, a line including two line conductors and a control conductor; a selector switch having access to said line; another selector switch connected to said line and including a relay having a winding and being operative to initiate operation of said other selector switch; an operating circuit for said relay including one terminal of a source of supply, a connection between said one supply terminal and one terminal of said winding, a connection between the other terminal of said winding and one of said line conductors, a loop including said first-mentioned selector switch and extending between said one line conductor and the other of said line conductors, a connection between said other line conductor and said control conductor in said other selector switch, and a connection between said control conductor and the other terminal of the source of supply derived in said first-mentioned selector switch. whereby no potential difference is present between said line conductors when said other selector switch occupies an idle position; and means for causing said first-mentioned selector switch to seize said line, thereby to complete said operating circuit.

23. In a telephone system, a line including two line conductors and a control conductor; a selector switch having access to said line; another selector switch connected to said line and including a relay having a winding and being operative to initiate operation of said other selector switch; an operating circuit for said relay including one terminal of a source of supply, a connection between said one supply terminal and one terminal of said winding, a connection between the other terminal of said winding and one of said line conductors, a loop including said firstmentioned selector switch and extending between said one line conductor and the other of said line conductors, a connection between said other line conductor and said control conductor in said other selector switch, and a connection between said control conductor and the other terminal of the source of supply derived in said firstmentioned selector switch, whereby no potential difference is present between said line conductors when said other selector switch occupies an idle position; and means for causing said first-mentioned selector switch to seize said line, thereby to complete said operating circuit; and means responsive to the operation of said relay for connecting the other terminal of the source of supply derived in said other selector switch to said control conductor.

24. In a telephone system, a first line, a selector switch having access to said first line, a second line, another selector switch connected to said first line and including a relay operative to initiate operation of said other selector switch, said other selector switch including a mechanism having an idle position and operative to select said second line, an operating circuit and a holding circuit for said relay, means for causing said first-mentioned selector switch to seize said first line, means responsive to the seizure of said first line for completing said operating circuit, means responsive to the operation of said relay for completing said holding circuit, means for causing a predetermined operation of said mechanism, and means responsive to said predetermined operation of said mechanism for interrupting said operating circuit.

25. In a telephone system, a first line, a first selector switch having access to said first line, a second line, a second selector switch connected to said first line and including a relay operative to initiate operation of said second selector switch, said second selector switch including a mechanism having an idle position and operative to select said second line, an operating circuit for said relay, means for causing said first selector switch to seize said first line, means responsive to the seizure of said first line for completing said operating circuit, means for interrupting said operating circuit, thereby to cause said relay to restore to release said second selector switch, means responsive to the restoration of said relay for causing a predetermined operation of said mechanism, means responsive to said predetermined operation of said mechanism for interrupting a further point in said operating circuit, and means for restoring said mechanism to its idle position.

26. In a telephone system, a first line, a selector switch having access to said first line, a second line, another selector switch connected to said first line and including a first relay and a second relay operative to initiate operation of said other selector switch, said other selector switch including a mechanism having an idle position and operative to select said second line, an operating circuit and a holding circuit for said first relay, means for causing said first-mentioned selector switch to seize said first line, means responsive to the seizure of said first line for completing said operating circuit, means responsive to the operation of said first relay for causing the operation of said second relay, means responsive to the operation of said second relay for completing said holding circuit, means for interrupting said operating and holding circuits, thereby to cause said first and second relays to restore to release said other selector switch, means responsive to the restoration of said first relay for causing a predetermined operation of said mechanism, means responsive to said predetermined operation of said mechanism for interrupting a further point in said operating circuit, and means responsive to the restoration of said second relay for interrupting a further point in said holding circnitandi'or'restorlngsaldmechanimtoits idle 2'7. Inaswltdihavingahanko! terminals, means for operating said switch to selcctanidlesetoiterminalsinsaidbanhmcans eflectiveuponselectionotanidlesetofterminms for connecting ground notential to the test terminaloltheselectedsetofterminnlaarelay individual to the selected set of terminals, and a grounded battery, one terminal of said selected setbeingnormally connectedthroughonewinding oi said relay to the non-grounded terminal of the battery, and another terminal of said selected set being normally connected through another winding of said relay to the test terminal said set.

28. In combination in a switching system, a battery, a. switch comprising a set of wipers and abank olterminalsmeansformovlngsaidwipers into engagement with any set of terminals in said bank, selectors, each of said selectors being connected to a different one of said sets of terminals, means associated with said switch and including the test wiper of said set of wipers for testing anengagedsetoiterminalsandforseizingan idle set of terminals, 9. line relay for each of said selectors, one terminal of web oi said sets of terminals being normally connected through one winding of the line relay 0! the associated selectortoonepoleofsaidbattery, anotherterminal of each of said sets being normally connected to one end of another winding of the line relay of the associated selector, and the test terminal of each of said sets being normally connected to the other end of the said other winding of the line relay of the associated selector, and a circuit closed upon seizure of any of said sets of terminals by said switch for operating the line relay of the selector connected to the seized terminals, said circuit including said battery, both windingsolsaidrelay,theterminaltowhichsaid onewindingoithelinerelayisnormallyconnected and including said other terminal and the test terminal to which the other winding of the line relay is normally connected.

29. In a combination according to claim 28, circuit means in each of said selectors eilcctlve upon operation of the line relay for opening the normally closed connection including said other winding and the test terminal.

30. In a cmnbination according to claim 28, circuit means in each of said selectors eiIective uponoperation oithelinerelay tor-opening the normally closed connection including said other winding and the test terminal and for connecting the other pole of said battery to said other winding to hold said relay operated. I

31. In a combination according to claim 28, circuit means in each oi said selectors effective upon operation of the line relay for opening the normally closed connectim including said other winding and the test terminal, and a circuit including said battery, both windings of said relay andbothterminalsoithesettowhlch theselectorisconnectedotherthaathctesttenninal for holding said line relay after th opening of the normally closed connection including said other winding and the test terminal.

32.1nacombinatlon tociaim28. ahlghreslstanceelementineachotsaldselectors, said element normally connecting said terminal otthebatterytothetstterminalofthesetto whichtheselectorisoonnectedandalsonormal- 1y said terminal 0! the battery to and said other terminal of the set to which the sem ,8 H. shunt 33. In ruiurill'un In a m battery, a switch comm-lain: asst oi wipers and abankotterminalameansi'ormovlngsaidnipus into emgment with any set oi terminals in saidbanhconnectorseanholssidbclngconnected toadiflerentoneotsaidsetsoi termlnaiameansassociatedwithsaldswltchwd including thetestwiperolsaldsetol'wlpernlor testinganengaged setoi'terminalsandim'leiningan idle set of terminals, a line relay for each ofsaid connectors, one terminal at each at said sets of terminals being normally connected through onewindingoitheline relayoltheassociated connector to one pole of said battery, another terminal of each of said sets being normallyconnectedtoone end oianotherwinding of the linereiay of the associated connector, and thetestterminaloieachoisaldsetsbdagnormally connectedto the other end of the saidother winding of the line relay of the associated connector, and a circuit closed upon seizure 01' any oi said sets of terminals by said switch for operating thelinerelay o! the connector connectcdto the seized terminals, said circuit including said battery,bothwindlngs oi said relay, the terminal towhichsaidonewindingolthelinerelayis normally connected and including the test terminaltowhiehtheotherwlndingoi'theiinerelay is nonnallyconnected.

34. In a combination according to claim 33, circuit means in each of said connectors eiloctive upon operation oi the line relay for opening the normally closed connection including said other winding and the test terminal.

35.1nacomblnation accordingtoclaim38, circuit means ineach of said connectors elective uponoperationofthelinerelayi'oropeningthe normally closed connection including said can windlngandthetestterminalandiorconnectimtheotherpoleoi saidhstterytosaidother windingtohold said relayoperated.

36.!nacombinationaccordingtoclaim33, circuitmeansineachotsaideflectiveuponoperation ofthelinerelaytorupening the normally closed connection including said throughsaldotherwiudingoi'thelinerelayto otherwindingandthetesttcrminahandadrmiitineludingsaidhattermbothwindingsotnid relayandbothterminaholtheaettowhlchthe oonnectorisconnectedotherthanthctesttuminal for holding said line relay operated alter the openlim oi the normally closed including said other winding and the ten terminal.

87. In a combination in a switching system. a batternaswitchcompflslngasetotwlneuand a bank oi. terminals. means for moving said wipersintoentwithanysetotterminalsin said baanlinkseachotsaidlinisbelmclmnectedtoadiflerentoneoisaidsctsoitermlnals, means associated with said switch and including thetestwiperoi'saidsetotwipemiortestlng an sctof termlnalsandlcrselalngan ldlesetoi'terminalaaiinerelaytoreacnotsaid linkaonetcrmlnalotecchofsaidsetsoitcrseizure 0! any of said sets of terminals by said switch for operating the line relay of the link connected to the seized terminals, said circuit including said battery, both windings of said relay, the terminal to which said one winding of the line relay is normally connected and including the test terminal to which the other winding of the line relay is normally connected.

38. In a combination according to claim 37, circuit means in each of said links effective upon operation 01 the line relay for opening the normally closed connection between said other winding and the test terminal.

39. In a combination according to claim 37, circuit means in each or said links eflective upon operation of the line relay for opening the normally closed connection between said other winding and the test terminal and for connecting the other pole of said battery to said other winding to hold said relay operated.

40. In a combination according to claim 37, circuit means in each of said links eflective upon operation of the line relay for opening the normally closed connection between said other winding and the test terminal, and a circuit including said battery, both windings of said relay and both terminals of the set to which the link is connected other than the test terminal for holding said line relay operated after the opening of the normally closed connection between said other winding and the test terminal.

41. In a switching system, lines, means comprising a switch and a link for use in connecting calling and called lines, said switch comprising a bank oi terminals and said link being connected to a set of terminals in said bank, means for connecting a calling line to said switch, means for operating said switch to test and seize the terminals to which said link is connected, a relay in said link, a circuit closed upon seizure of said link for operating said relay, said circuit including said calling line, the two line terminals and also the test terminal of said set 0! terminals, and a circuit closed responsive to the operation of said relay for holding said relay operated, said holding circuit including said calling line and the two line terminals but excluding the test terminal of said set of terminals.

NORMAN H. SAUNDERS.

Disclaimer Re. No. 21,768.N0rmrm H. Saunders, Chicago, Ill. TELEPHONE SYSTEM. Patent dated Apr. 8, 1.941. Disclaimer filed Sept. 8, 1950, by the assignee, Automatic Electric Laboratories, Inc.

Hereby enters this disclaimer to claim 5 of said patent.

[Ofiicial Gazette October 3, I 950] 

